<!DOCTYPE html>
<html>
  <head>
    <meta charset="UTF-8">
    <title>Document</title>
  </head>
  <body>
    <script>
      function Person() { }
      console.log(Person.prototype.__proto__ === Object.prototype); // true
      var obj = {};
      console.log(obj.__proto__ === Object.prototype);              // true
      console.log(Object.prototype.__proto__);                      // 输出结果：null
    </script>
  </body>
</html>